Normal Menstrual Cycle

Topic Overview

What is a menstrual cycle?

The menstrual cycle is
the series of changes a woman's body goes through to prepare for a pregnancy.
About once a month, the
uterus grows a new lining (endometrium) to get ready
for a fertilized egg. When there is no fertilized egg to
start a pregnancy, the uterus sheds its lining. This is the monthly
menstrual bleeding (also called menstrual period) that women have from their early
teen years until
menopause, around age 50.

The menstrual
cycle is from Day 1 of bleeding to Day 1 of the next time of bleeding. Although
the average cycle is 28 days, it is normal to have a cycle that is shorter or longer.

Girls usually start having menstrual periods between the ages of 11 and
14. Women usually start to have fewer periods between ages 39 and 51. Women in
their 40s and teens may have cycles that are longer or change a lot. If you are
a teen, your cycles should even out with time. If you are nearing menopause,
your cycles will probably get longer and then will stop.

Talk to
your doctor if you notice any big change in your cycle. It's especially
important to check with your doctor if you have three or more menstrual periods that last
longer than 7 days or are very heavy. Also call if you have bleeding between
your periods or pelvic pain that is not from your period.

What controls the menstrual cycle?

Your hormones
control your menstrual cycle. During each cycle, your brain's
hypothalamus and
pituitary gland send hormone signals back and forth
with your
ovaries. These signals get the ovaries and uterus
ready for a pregnancy.

The hormones
estrogen and
progesterone play the biggest roles in how the uterus
changes during each cycle.

Estrogen builds up the lining of the
uterus.

Progesterone increases after an ovary releases an egg
(ovulation) at the middle of the cycle. This helps the
estrogen keep the lining thick and ready for a fertilized egg.

A
drop in progesterone (along with estrogen) causes the lining to break down.
This is when your period starts.

A change in hormone levels can affect your cycle or
fertility. For example, teens tend to have low or changing progesterone levels.
This is also true for women close to menopause. That is why teens and women in
their 40s may have heavy menstrual bleeding and cycles that change in
length.

Other things can change your cycle. They include birth
control pills, low body fat, losing a lot of weight, or being overweight.
Stress or very hard exercise also can change your cycle. Pregnancy is the most
common cause of a missed period.

What common symptoms are linked to the menstrual cycle?

Some women have no pain or other problems. But other women have symptoms
before and during their periods.

For about a week before a period,
many women have some
premenstrual symptoms. You may feel more tense or
angry. You may gain water weight and feel bloated. Your breasts may feel
tender. You may get acne. You also may have less energy than usual. A day or
two before your period, you may start having pain (cramps) in your belly, back,
or legs. These symptoms go away during the first days of a period.

When your ovary releases an egg in the middle of your cycle, you may have
pain in your lower belly. You also might have red spotting for less than a day.
Both are normal.

How can women take care of bleeding and symptoms?

You can use pads, tampons, or menstrual cups to manage bleeding. Whatever you use, be
sure to change it at least every 4 to 8 hours.
Pads may be best at night.

Many women can improve their symptoms
by getting regular exercise and eating a healthy diet. It also may help to
limit alcohol and caffeine. Try to reduce stress.

A heating pad, hot water bottle, or warm bath also can help
with cramps. You can take an over-the-counter medicine such as ibuprofen or
naproxen before and during your period to reduce pain and bleeding.

Normal Menstrual Cycle

The menstrual cycle is the
series of changes your body goes through to prepare for a possible pregnancy.
About once a month, the
uterus grows a new, thickened lining (endometrium)
that can hold a
fertilized egg. When there is no fertilized egg to
start a pregnancy, the uterus then sheds its lining. This is the monthly
menstrual bleeding (also called menstruation or menstrual period) that you have
from your early teen years until your menstrual periods end around age 50
(menopause).

The menstrual cycle is measured from
the first day of menstrual bleeding, Day 1, up to Day 1 of your next menstrual
bleeding. Although 28 days is the average cycle length, it is normal to have a cycle that is shorter or longer.

A teen's cycles may be long (up to 45
days), growing shorter over several years.

Between ages 25 and 35, most women's cycles are regular, generally
lasting 21 to 35 days.

Around ages 40 to
42, cycles tend to be the shortest and most regular. This is followed by 8 to
10 years of longer, less predictable cycles until menopause.

Three phases of the menstrual cycle

The phases of
your menstrual cycle are triggered by hormonal changes.

Menstrual period

On Day 1 of your cycle, the
thickened lining (endometrium) of the uterus begins to
shed. You know this as menstrual bleeding from the vagina. A normal menstrual
period can last 4 to 6 days.

Most of
your menstrual blood loss happens during the first 3 days. This is also when
you might have cramping pain in your pelvis, legs, and back. Cramps can range
from mild to severe. The cramping is your uterus contracting, helping the
endometrium shed. In general, any
premenstrual symptoms that you've felt before your
period will go away during these first days of your cycle.

Follicular phase

During the follicular phase, an
egg follicle on an
ovary gets ready to release an egg. Usually, one egg
is released each cycle. This process can be short or long and plays the biggest
role in how long your cycle is. At the same time, the uterus starts growing a
new endometrium to prepare for pregnancy.

The last 5 days of the
follicular phase, plus ovulation day, are your
fertile window. This is when you are most likely to
become pregnant if you have sex without using
birth control.

Luteal (premenstrual) phase

This phase starts on
ovulation day, the day the egg is released from the
egg follicle on the ovary. It can happen any time from Day 7 to Day 22 of a
normal menstrual cycle. During ovulation, some women have less than a day of
red spotting or lower pelvic pain or discomfort (mittelschmerz). These signs of
ovulation are normal.

If the egg is fertilized by sperm and then
implants in (attaches to) the endometrium, a pregnancy begins. (This pregnancy
is dated from Day 1 of this menstrual cycle.)

If the egg is not
fertilized or does not implant, the endometrium begins to break down.

After the teen years and before
perimenopause in your 40s, your luteal phase is very
predictable. It normally lasts 13 to 15 days, from ovulation until menstrual
bleeding starts a new cycle. This 2-week period is also called the
"premenstrual" period.

Many women have premenstrual symptoms
during all or part of the luteal phase. You may feel tense, angry, or
emotional. You may gain water weight and feel bloated. Or you may have tender
breasts or acne. A day or more before your period, you may start to have pain
(cramps) in your abdomen, back, or legs. It is normal to have less energy at
this time. Some women also have headaches, diarrhea or constipation, nausea,
dizziness, or fainting.

Menarche and the Teenage Menstrual Cycle

Menarche
(say "MEN-ar-kee") is a girl's first menstrual period. A first period usually
happens after breasts, pubic hair, and underarm hair have begun to grow. Menarche is a sign of growing up and becoming a woman. It can happen as early as about age 9 or up to age 15. The first few periods are usually light and irregular. About 2 out of 3 girls have a regular pattern
of menstrual periods within 2 years of menarche.footnote 1 During the teen years, periods may become longer and heavier. For more information, see Menarche.

Perimenopausal Menstrual Cycle

Perimenopause,
which means "around menopause," refers to the 2 to 8 years of changing hormone
levels and related symptoms that lead up to
menopause. The most common sign of perimenopause is
longer, often irregular menstrual cycles that are caused by hormonal ups and
downs.

Most women start perimenopause between ages 39 and
51. Some women begin to notice menstrual changes and
premenstrual syndrome (PMS) symptoms in their late 30s
when hormones begin to fluctuate and fertility naturally declines. Other women
don't notice perimenopausal changes until their late 40s.

Perimenopause is a time of unpredictability. Menstrual and
hormone-related symptoms are different for every woman. Some notice few or no
changes. And others have severe symptoms that disrupt their sleep and daily
lives. As during the teen years, irregular cycles can lead to
heavy menstrual bleeding. Other common symptoms
include mild to severe
hot flashes,
insomnia, cloudy thinking, headaches, heart
palpitations, mood swings, irritability, depression, and anxiety. Some of these
symptoms can also be related to aging and other life changes. See your doctor
to discuss your symptoms, whether you want symptom treatment, and which
therapies you can consider.

See a doctor for menstrual bleeding
that lasts longer than 7 days or for cycles that are shorter than 21 days or
longer than 35 days.

You can improve your body's ability
to handle menstrual changes by getting regular exercise, eating a healthy diet,
limiting alcohol and caffeine intake, and reducing stress. Nonprescription pain
relievers can also help reduce some symptoms.

Medicine for menstrual pain and bleeding

Try a
nonprescription medicine to help relieve your pain and bleeding. Start taking
the recommended dose of pain reliever when symptoms begin or 1 day before your
menstrual period starts. If you are trying to become pregnant, talk to your
doctor before using any medicine. Be safe with medicines. Read and follow all instructions on the label.

Managing menstrual bleeding

You can choose from
a range of pads, tampons, or menstrual cups to manage menstrual bleeding. Follow all
directions included with the product of your choice.

Pads range from thin and light
to thick and superabsorbent. They protect your clothing, with or without using
a tampon. Pads may be your best choice for use at night.

Tampons range from small to large, for light to heavy flow.
You can place a tampon in the vagina by using a slender tube (that is packaged
with the tampon) or by tucking it in with a finger. Be sure to change a
tampon at least every 4 to 8 hours. This helps prevent leakage and infection.

Menstrual cups are inserted in the vagina to collect menstrual flow. You remove the menstrual cup to empty it. Some are disposable and some can be washed and used again.

Whichever you use, be sure to change it regularly.
Tampons or menstrual cups are ideal for activities that pads aren't practical for, such as
swimming. They should be changed at least every 4 to 8 hours, so they may not work as well for nighttime use. It may take some experimenting to find the right products for you.

When to Call a Doctor

There is a broad range of
"normal" among menstruating women. Unpredictable or long
menstrual cycles are normal for teenagers and women in
their 40s. For teens, a normal cycle can be as short as 21 days or as long as
45 daysfootnote 2. If you are a teen, you can expect cycles to even out over time. If you
are nearing the age of menopause, you can expect menstrual cycles to become
longer and eventually to stop. If you are not a teen and you are not older than
40 and your cycles are shorter than 21 days or longer than 35 days, there is a
chance that you have a problem that needs to be checked by your doctor.

You will need a medical check by a doctor if you have any change in your
menstrual pattern or amount of bleeding that affects your daily life. This
includes menstrual bleeding, for three or more menstrual cycles, that:

Lasts longer than 7 days.

Is a
sudden or big change from your usual period.

Is very heavy. This
means that you are passing large clots or soaking through your usual pads or
tampons each hour for 2 or more hours.

Other symptoms you need to have checked include:

Bleeding between menstrual periods.

Pelvic pain that
is not linked to menstrual bleeding and lasts longer than a day.

If you are a teenage girl, see your doctor if you have not
started having periods by age 15.

References

Citations

American Academy of Pediatrics, American College of
Obstetricians and Gynecologists (2006, reaffirmed 2009). Menstruation in girls and adolescents:
Using the menstrual cycle as a vital sign. Pediatrics,
118(5): 2245-2250.

Other Works Consulted

American Academy of Pediatrics, American College of
Obstetricians and Gynecologists (2006, reaffirmed 2009). Menstruation in girls and adolescents:
Using the menstrual cycle as a vital sign. Pediatrics,
118(5): 2245-2250.

American Academy of Pediatrics, American College of
Obstetricians and Gynecologists (2006, reaffirmed 2009). Menstruation in girls and adolescents:
Using the menstrual cycle as a vital sign. Pediatrics,
118(5): 2245-2250.

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